2012 Volume 24 Issue 1 Pages 1-9
Influence of the thermal history during injection molding of linear low density polyethylene (LLDPE) on the formation of unpleasant taste was investigated for assuring the taste of beverage in vending machines. LLDPE samples were molded using antioxidants; BHT, Irganox 1010, D, L-α-tocopherol and Irgafos 168. Tastes of soaked water of the samples were individually different, and such tastes were thereby responsible for the antioxidants. Furthermore, the tastes were changed when free chlorine (0.3 ppm) was added for sterilization. The antioxidants and their degraded products were identified in the soaked water as candidates of the unpleasant tastes by gas chromatography/mass spectrometry (GC/MS). Tastes of the identified compounds were evaluated by sensory test to determine their threshold concentrations for estimation of contribution to the unpleasant taste. From the thermal behavior of the antioxidants examined by thermogravimetry/differential thermal analysis (TG/DTA), decomposition of the antioxidant was observed in the temperature range of the molding. Moreover, formation of volatile compounds under the condition was evidenced by pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The present study revealed that controlling the thermal history during molding is important to assure the quality of taste of beverage being contacted with the molded LLDPE, as well as general thermoplastics in vending machine.
